Bacterial Cell Structure Flashcards
what is morphology
have to consider shape + arrangement
describe coccus/cocci and state the 5 arrangements possible
- round & spherical
- diplococci (two cells stuck together)
- streptococci (chain-like arrangement)
- tetrad (four cells stuck together)
- sarcinae (eight cells stuck together)
- staphylococci (grape-like clusters)
describe bacillus/bacilli and state the 4 arrangements possible
- rod shaped cells
- single (one bacillus)
- diplobacilli (two bacillus stuck together)
- streptobacilli (many bacilli stuck end to end)
- coccobacillus (blobby rod shape)
describe curved/spiral and state the 3 arrangements possible
- spiral
- vibrio (curved rods)
- spirillum (short, rigid spirals)
- spirochete (long, flexible spirals)
3 less common morphologies
- filamentous bacteria
- fruiting bodies (blobs on a stick)
- biofilms
pleomorphic
bacteria change morphology depending on enviro/cell state
describe influence of cell size
smaller size = larger SA / volume ration
- easier for nutrients to move in and wastes to move out
- faster growth/ evolution
what are the 4 structures shared by all bacteria
- cytoplasm
- ribosome
- plasma membrane
- nucleoid containing DNA
what is the cell envelope
= plasma membrane and all layers external to it
- plasma membrane
- cell wall
- external layers
what does the plasma membrane consist of?
- phospholipids
- hopanoids
- various proteins
- glycolipids
- oligosaccharides
what do sterols/ hopanoids do in the plasma membrane and which are found in pro vs euk
maintain the fluidity and structure of the membrane
sterols = euk (cholesterol)
hopanoids = pro (bacteria)
the plasma membrane regulates ……….
regulates transport in/ out of the cell
passive diffusion
substances move across membrane with concentration gradient
- does NOT require energy or proteins
facilitated diffusion
move with concentration gradient with help of integral membrane proteins
- NO atp needed
active transport
moved against concentration gradient
- requires ATP
what substances can travel via passive diffusion vs facilitated
passive = small, nonpolar, not charged
facilitated = large, polar, charged
primary vs secondary active transport
primary = uses energy from ATP hydrolysis to move substances across membrane
secondary = uses energy from another molecule
- both require changes to integral proteins to provide a channel of travel
group translocation
molecules are modified as they enter the cell
what do cell walls do in bacteria
provide bacteria with structure and protection
-rigid
-porous
-peptidoglycan
gram staining separates cell walls based on ______ content
peptidoglycan content
gram positive vs gram negative vs atypical
gram positive = one membrane, thick peptidoglycan layer (purple)
gram negative = two membranes, thin peptidoglycan layer (pink)
atypical = neither structure
overall charges of gram + & -
~ where do they get these charges from?
BOTH negative!
(+) from teichoic and lipoteichoic acids
(-) from LPS (lipopolysaccharide)
gram + are really susceptible to _____ because…..
to penicillin as they have no outer membrane
cell walls are essential to cell survival as they keep …..
keep from osmotic lysis in isotonic conditions !
does having a cell wall protect a cell in hypertonic conditions?
no not fully
atypical gram positive bacteria
mycobacterial cell walls
- inner membrane, peptidoglycan, outer membrane
- in outer membrane there is mycolic acid which holds the purple color
atypical gram negative bacteria
do not retain purple color
- inner and outer membrane with NO peptidoglycan layer
- stains pink
what does lysozyme do
breaks B1-4 linkages which destroys peptidoglycan (will not retain purple)
what emerges from membranes and what do they do
EVs
extracellular vesicles
they carry cargo thru extracellular enviro to fuse with other cells
how do EVs get thru the cell wall
osmotic pressure pushes out membrane through gaps/pores in peptidoglycan
what differentiates EVs from cells
EVs = no full genome, cannot undergo metabolic reactions
what would u expect in gram + EVs vs gram - EVs ?
+ = plasma membrane surrounding cytoplasm
- = outer membrane budding out
types of external layers
glycocalyx (sugar) coatings:
- slime layers
- capsules
(bacteria)
protein coatings:
- S-layers
(archaea)
what are slime layers
- allows for attachment to surfaces and other cells (shared)
- allows for motility
- can live together in biofilms
capsules
- only associated with cell that made it
- no motility
- can adhere to surfaces
- protect cell from dehydration, phagocytosis
capsules are ____ to both negative and simple stain so it will be _____ after
resistant to both stains and will be colorless after
what are s-layers
present mostly archaea
- made of proteins
- provide structure
- self assembles
describe the cytoplasm
- very crowded
- contains cytosol (liquid) & soluble molecules
describe cytoskeleton
- some bacteria have similar structures to those of euk proteins
tubulin homologues = FtsZ
(cell devision)
intermediate homologues = CreS
(gives vibrio shape)
actin homologues = MreB
(give cell rod shape)
which prokaryote has eukaryotic actin cytoskeleton proteins
archaeal cell Loki type bacteria
intracytoplasmic membranes
not the same as membrane bound organelles
- more SA = more ATP synthesis
inclusions and the 4 types
used for storage
- PHA/B granules = store hydrocarbons
- phosphate globules = store components for making nucleic acids
- sulfur globules = store H2S to be used in metabolism
- gas vacuoles = allow to regulate buoyancy
why would bacteria store items in inclusion bodies
- protecting inside from enviro
- easier to keep track of stores
- concentrated amount in one area
ribosome difference in bacteria vs euk and why does this make them a good target for antibiotics
do the same job just bacteria are slightly smaller and 70S not 80s
good as antibiotics would only be specific to and recognize bacteria not euk so wouldn’t harm human cells
bacteria structure
circular genome
- single double stranded
plasmids
not part of chromosome
- circular double stranded DNA
- makes something transmissible
what external structures are used for attachment and motility
attachment:
- pili = attach cell to cell
- fimbriae = attach cell to surface
(short)
motility:
- flagella = allow cells to move around
(long)
mono,lopho and peritrichous flagella
monotrichous = single hairlike
lopho = tuft of flagella
perit = all angles covered by flagella
how do bacteria decide when and how to move?
move in response to stimuli:
- chemotaxis = moving toward/ away from chemical stimuli
- phototaxis = moving toward/ away from light stimuli
many use tumble and run movement (travel in random directions)
describe endoscopes
formed by SOME gram + bacteria
- soil bacteria
- NOT a method of reproduction
- cell is dormant in extreme conditions
sporulation vs germination
sporulation = forming endospores is triggered by cell stress
germination = reaches favourable conditions
